Magnetic particle coupling device with nickel and nickel-coated iron particles



Oct. 15, 1957 F. e. LOGAN EIAL 2,309,732

I MAGNETIC PARTICLE COUPLING DEVICE WITH mom.

AND NICKEL-COATED IRON PARTICLES Filed Nov. 16, 1950- 8 NICKEL-COATEDIRON 3o PARTICLES NICKEL 1 8 PARTICLES INVENTORS FRANK G. LOGAN DAVID W.RAU

aft 4 z 7 1 AII'TORNEY MAGNETIC PARTICLE COUPLING DEVICE WITH NICKEL AWNICKEL-COATED RON PAR- TICLES Frank G. Logan and David W. Ran, Kirkwood,Ma assignors to Vickers Incorporated, Detroit, Mich, a corporation ofNlichigan Application November 16, 1950, Serim No. 1%,060

7 Claims. (Cl. 192-215) The invention relates to power transmission andmore particularly to power transmission by magnetic coupling through themedium of magnetic particles.

The invention herein is concerned with the type of magnetic couplingprovided between two relatively movable spaced coupling membersseparated by a gap in which magnetic particles act to transmitmechanical force between the coupling members when the gap material(magnetic particles) is magnetically excited. Magnetic clutches, brakes,drives, etc., are examples of the use of this type of magnetic coupling.

Since one of the limiting factors of any coupling device, such as aclutch, brake, or drive, is the amount of heat it can successfullydissipate, it is desirable that material in the gap of a magneticcoupling device have a high thermal conductivity in order to effectivelytransfer heat across the gap to the exterior of the device. Othercharacteristics desirable to have in a gap material are as follows:smooth application and transmission of force; reasonably highpermeability in order to transmit force with the least amount of controlcurrent; resistance to packing and sintering either of which may preventpower transmission or cause the coupling members to seize depending onthe volume of the gap material; chemical and magnetic stability over areasonable period of time.

Prior to the invention herein, iron particles were the only magneticparticles which achieved any practical success as gap material inmagnetic coupling devices. Iron particles, known commercially asCarbonyl E, which are spongy particles of the order of eight microns,have been extensively used in such devices. However, iron particlesalone cannot be used in magnetic coupling devices because they pack andsinter after a short time.

For example, in a clutch iron particles alone, such as Carbonyl Ewithout any additive, produce high initial torque for only a short timebefore the particles sinter or pack into a mass which will cause eithercomplete failure of torque transmission or locking of the couplingmembers. What happens depends largely on the proportion of the gapmaterial to the gap volume.

"Several proposals made in the past have retained the use of ironparticles while alleviating to some degree the sintering and packingproblems. These proposals involve mixes of iron particles with eitherliquid or solid lubri cantssuch as oils, silicone fluids, graphite,etc., all of which brought their own special problems and disadvantages.

Both liquid and solid lubricants possess no magnetic characteristics andconsequently when mixed with iron dilute the permeability and magneticefiectiveness of the iron on a volume basis. A mixture of iron particlesand the lubricant, either liquid or solid, necessarily has much lowerpermeability than an equivalent volume of iron particles without theadditive. In rotary applications employing liquid mixtures with ironparticles, packing is'often caused by centrifuging, resulting in someloss of torque in many cases. An added disadvantage is the liquidsealing problem encountered with mixtures of iron particles and liquids.Graphite and other solid lubricants have such a low thermal conductivitythat the heat transfer across the magnetic gap is very poor when the gapmaterial is a mixture of iron particles and a solid lubricant, therebylimiting the power that can be dissipated by a device of a particularsize.

The present invention contemplates the use of iron particles in a gapmixture that will not sinter or pack under operating conditions andwhich does not require either liquid or solid lubricants. This isaccomplished in accordance With the invention by applying a nickel coatto the iron particles and mixing these particles with nickel particles.Thus the present invention embraces the use of nickel-coated ironparticles mixed with nickel particles as a gap material in connectionwith magnetic coupling devices. 7

An object of this invention is to provide a new and useful magneticcoupling device wherein the gap material has substantially the followingcharacteristics: reasonable permeability to allow effective applicationand transmission of force with reasonable magnetic excitation;resistance to sintering and packing under operating conditions; highthermal conductivity; freedom from sealing problems like thoseencountered with liquid mixtures; chemical and mechanical stability fora reasonably long period of time.

Further objects and advantages of the present invention Will be apparentfrom the following description reference being bad to the accompanyingdrawing wherein a preferred' form of the present invention is clearlyshown.

In the drawing:

i The single figure in the drawing is a view partly in cross sectionillustrating the use of the invention as embodied in an electro-magneticclutch.

Within the sphere of the invention the coupling members may adoptvarious forms of construction; the gaps therebetween may be single orcompound and of any suitable form, e. g. in rotary applications the gapsmay be radial, axial, or combinations of both; the magnetic excitationacross the gaps between the coupling members may be provided in avariety of ways, such as fixed magnets with or without variable shuntcontrol, current carrying magnetizing coils etc., any of which may becarried by any of the coupling members, by a yoke independent of thecoupling members, or any other suit able manner; and any of the couplingmembers may be employed either as force transmitting or force receivingmembers.

In accordance with one embodiment of the invention, shown in the drawingby way of example and not as limiting the invention or the scopethereof, a magnetic clutch includes a pair of relatively movablecoupling members 10 and 11 separated by a magnetizable air gap 12 inwhich is disposed a quantity of nickel particles and nickel-coated ironparticles as indicated by the legend in the drawing. Magnetic excitationbetween the members 10 and 11 across the gap 12 is provided by amagnetizing coil 13 carried by the member 19 as later described. Themember 14), which is completely surrounded by the member 11, is fixed toa shaft 15 and includes a magnetic yoke made of two disks 14 and 16 madeof suitable magnetic material, for example, steel or iron. Centralsections of the disk surrounding shaft 15 abut each other as indicatedat 18 to form a low reluctance joint, and annular grooves 20 and 22 areformed in the disks to receive the magnetizing coil 13.

The disks are spaced apart from their outer diameter to the grooves 20and 22, and the gap between them is sealed by a nonmagnetic ring spacer26 flush with the peripheral surfaces 28 and 3% of the disks, whichsurfaces are the pole faces of the magnetic yoke. It will be seen fromthe figure that the cross section of the yoke Patented Oct. 15, 1957 =2is generally U-shaped, the legs being the spaced sides ofthe disks 14and 16 whose abutting sections formthe base of the U. Thus, when theyoke is magnetized upon energization of the coil, an infinite number ofhorseshoe magnets form a volume of revolution'aroundthe shaft 15..

Leads 32 and 34 from the coil 13' are brought out through a smallopening 36 at the joint 18 and .anaxial slot 38 in the shaft 15, and areconnected to a pair of slip rings 40 and 42 mounted on an insulator disk44 fixed to rotate with the shaft 15. A pair of brushes 46 and 48contacting the rings 40 and 42, respectively, may be connected to asuitable source 50 of control current through a rheostat 52. The pathof. control current to.

the magnetizing coil 13 is obvious fromthe figure.

The member 11 includes a finned ring 54 formed from suitable magneticmaterial, such .as, iron. or steel, and

carried by non-magnetic. end bells 56 and 58 mounted.

on ballbearings 60 and 62 for rotation aroundtheshaft 15. Bearingretaining rings 64 and 66 may be provided. with suitable seals 68 and 70to prevent, the .escape of magnetic particlesfrom the clutch interior.to the bear-. ings. A flanged union 72 secured to the end bell 58 provides coupling means to shaft 74 which may be keyed to the union 72 inany suitable manner., A suitable.

filler hole 76 and plug 78 are provided in theend bell 58 to permit theintroduction of the magnetic particles into the interior of the clutch.

Either of the members and 11 may be interchange.

ably employed as a driver or a driven member, for ex-.

ample if the inner member 10 is connected through shaft to a prime moverthen the outer member 11', together with the shaft 74, become the outputmembers of the clutch. Suitable labyrinth mazes, or bafiles may beprovided if desired between the coupling members to prevent the gapmaterial from falling or working toward shaft portions of the apparatusand to keep the particles.v

close to the gap when the members are at standstill or at slow speed andthe coil 13 is de-energized.

Finely divided nickel is obtainable commercially: as' nickel powder andmay be made by any suitable meth-.

od; for example, by the Schoup metalizing process, which is a form ofmetal spraying that produces atomized.

,nickel which may be conveniently collected by aiming the spray into acardboard box.

Although any type of magnetic iron particles may be.

used in the practice of the invention, magnetic iron par ticlescommercially known asCarbonyl E, Carbonyl L, and Kurt-Orban S3 arepreferred forms. Foruse. in

practicing the invention the iron particles may be coated with nickel byany suitable method, for example by plat.-

ingf'One' plating method which was used to coat nickel on ironparticlesemployed in the practice of the present invention is known as theelectroless plating method.

A particular mixture. which worked very satisfactorily as gap'materialin the practice of the invention comprised equal parts by weight ofnickel particles of an order, less than 54 microns (pass through 270sieve) and nickel-,

coated Kurt-Orban S3 iron particles of about the same order. Thisexample is merely illustrative, and the ratio.

of the components and relative sizes of the particles may be varied asdesired. The type of duty and the nature. of the, coupling device arefactors which are necessarily. considered in determining the size of theparticles, their respective proportions, and the quantity thereof withrela-- magnetic members 14, 16, and 54 become magnetizedv when themagnetic field is established and the magne-, tized particles bind thedriving and the driven member together to an extent dependent on thestrength of the field and the load. Operative ranges from substantially.

% slip to zero slip (synchronous operation) between the coupling membersis available through control of the magnetic excitation. For use as abrake, one of the movable members may be held rigid. For example, themember with the coil may be stationary and utilized to brake therotating member 11.

Magnetic particle clutches employing a mixture of nickel-coated ironparticles and nickel particles have'been successfully operatedcontinuously for many hours with-. out sintering, packing, wear, ordeterioration of the magnetic stability taking place.

Although, only one embodiment has been illustrated, the invention isapplicable wherever a magnetic coupling is required between spacedmagnetic members, such as, magnetic clutches, brakes, etc. Further, theinvention is not confined to rotating machinery but is equally adaptableas a coupling between magnetic members, relatively movable in other thanrotative paths, for exampl rectilinear motion, etc.

Whilethe form of embodiment of the invention as herein disclosedconstitutes a preferred form, it is to be understood that other formsmight be adopted, all coming within the scope of the claims whichfollow.

What is claimed is as follows:

1. Means for establishing a connection to transmit me-. chanical forcefrom one to another of a pair of spaced relatively movable couplingmembers defining a gap therebetween, said means comprising means forestablishing a magnetic field across said gap and a dry particle mixture including discrete nickel-coated iron particles and discrete nickelparticles disposed in said gap and effective, in response to magneticexcitation, to establish a connection for transmitting mechanical forcebetween said coupling members.

2. A gap material for magnetic coupling devices consisting essentiallyof an unlubricated mixture of substan-.

tial proportions of discrete nickel-coated iron particles and discretenickel particles,

3.. Means for forming a force-transmitting bond be-- tween a pair ofspaced relatively movable coupling mem-.

bers'defining a gap therebetween, said means comprising.

means for establishing a magnetic field across said gap and unlubricatedmagnetic particles in said gap and responsive to said field forestablishing a force-transmit-.

for establishing a force transmitting bond between said' members,whereby movement of one member at least. tends to cause movement of theother member, said magnetic particles including discrete nickel-coatediron par-. ticles and discrete nickel particles.

.. 5. A magnetic coupling device comprising a pair of.

spaced relatively rotatable coupling members defining a gaptherebetween, means for'establishing a magnetic field across said gap,and dry particles in said gap and re-.-

sponsive to said field for establishing a force-transmitting bondbetween said members, whereby rotation of one member ,at least tends tocause rotation of the other: member, said particles consistingessentially'of discrete nickel-coated iron particles and discrete nickelparticles.

6. Means for forming a force-transmitting bond -be-.

tween a pair. of spaced relatively rotatable couplingmembers defining agap therebetween, said means comprising means for establishing amagnetic field across said gap and unlubricated magnetic particles insaid gap and responsive to said field for establishing a forcetransmitting bond between said members whereby rotation of one member atleast tends to cause rotation of the other member, said magneticparticles consisting essentially of substantial proportions of discretenickel-coated iron particles and discrete nickel particles.

7. A magnetic coupling device comprising a pair of spaced relativelyrotatable coupling members defining a gap therebetween, means forestablishing a magnetic field between said members at said gap, andunlnbricated magnetic particles in said gap and responsive to said fieldfor establishing a force-transmitting bond between said members, wherebyrotation of one member at least tends to cause rotation of the othermember, said magnetic particles including discrete nickel-coated ironparticles and discrete nickel particles.

References Cited in the file of this patent UNITED STATES PATENTS711,123 Rhoades Oct. 14, 1902 6 1,915,386 'Schumacher et al June 27,1933 1,986,197 Harshaw Jan. 1, 1935 2,519,449 Findley Aug. 22, 19502,525,571 Winther Oct. 10, 1950 2,575,360 Rabinow Nov. 20, 19512,596,654 Clark et a1 May 13, 1952 2,629,471 Rabinow Feb. 24, 1953FOREIGN PATENTS 261,748 Switzerland Sept. 1, 1949 OTHER REFERENCESTechnical Report 1213, National Bureau of Standards, Washington, D. C.,March 30, 1948.

Magnetic Clutch holds M. P. A. Interest; Chemical and Engineering News,vol. 27, No. 17, April 25, 1949.

